The present invention relates to a multi stage cold forging machine, and more particularly, to a cold forging machine which forms metal parts such as bolts through a series of stages, wherein the machine includes a device (hereinafter called a parts forming aid unit) for aiding small parts, such as bolts having short shanks, to be stably clamped by chucks.
A multi stage forging machine is known in the art, which forms metal parts progressively as a blank is transferred from stage to stage. The machine employs chucks for clamping a blank and transferring it from one die to the next. At each stage the blank is pushed out of the die by a knockout pin which moves synchronously with the withdrawal of the forging hammers.
The known multi-stage forging machine encounters a problem when small parts (i.e. ones having short shanks) are forged. Now, referring to FIG. 10, the problem will be explained:
FIG. 10 shows two cases (I) and (II) where a long bolt (a.sub.1) and a small bolt (a.sub.2) are forged, respectively. The small bolt (a.sub.2) has a short shank (a.sub.2) as compared with its head. The small bolt (a.sub.2) is pushed out of the die by a knockout pin (c) more quickly than the long bolt (a.sub.1), so that the chuck (d) must quickly catch the small bolt (a.sub.2). Otherwise, it would slip out of the die. In contrast, the long bolt (a.sub.1) takes a longer time before it comes out of the die (b), thereby enabling the chuck (d) to have sufficient time to catch the bolt (a.sub.1). When the forging metal parts are small, the chucks have the difficulty of transferring them from stage to stage.
The present invention is directed toward a multi-stage cold forging machine which solves the problems discussed above with respect to the known multi-stage cold forging machines. Thus an object of the present invention is to provide an improved multi-stage cold forging machine capable of forming metal parts of any size without breaking the continuity of processes throughout the series of stages.
The object of the present invention is achieved by providing a multi-stage cold forging machine including a parts forming aid unit, the aid unit having a number of aid pins corresponding to that of the forging dies, the pins being adapted to retain a blank against a knockout pin slidable in the dies, and transfer it from one stage to the next, wherein the aid pins are operated in such a manner as to stand out of the way of the forging hammers moved by a ram. Thus the blank is progressively refined as it is transferred from stage to stage.
Other objects and advantages of the present invention will become more apparent from the following detailed description, when taken in conjunction with the accompanying drawings which show, for the purpose of illustration only, one embodiment in accordance with the present invention .